![]() ![]() That assumes your main lobe is exactly aligned with the bore-sight axis of your antenna though, and that's not always true. You could, in principle, do the same thing using a compass and inclinometer, if you trust the compass and inclinometer to be accurate enough. Track the sun, peak sun noise, and compare the reading you get on your AZ and EL readouts to the numbers generated by EMECalc. However to get that correction data in the first place, you need a multi point calibration. Even if everything isn't perfectly aligned, as long as you know your deviation from the expected reading at any point, you can compensate and you still only need a single calibration point. If your main support mast is truly vertical and your AZ and EL axes are at exactly 90 degrees and your AZ and EL readout systems are accurate and linear, then you only need a single calibration point. ![]() ![]() If you do this throughout a day, you can get multiple points. Of course that only gives you a since point. If you peak sun noise, you know exactly were your antenna is pointed and you can compare your EL and AZ readout with the sun's known position. A program like EMECalc will give you the Elevation and Azimuth of the sun at any time. Probably the best way to get a single point calibration is by peaking the system on sun noise. So how to you calibrate your dish pointing system and how do you know when it's out of calibration? On 432, with 4 x 9-wavelength yagis, you'd want to be within about 2 degrees of the moon to maximize gain (3dB beamwidth would be around 12 degrees). The same numbers would be true for any antenna with a gain of around 27-28dBm. If you're 2 degrees off the moon you'll lose about 1.5dB and if you're 3 degrees off you'll lose close to 3dB. A 1 degree pointing error will result in a signal loss of less than 0.5dB. In fact you really need to be within 1 degree of the moon if you want to get close to the maximum signal. This doesn't mean you need to be within 6 degrees of the moon, it doesn't even mean you need to be within 3 degrees of the moon (the half beam width). A 3m dish at 1296 has a 3dB beamwidth of around 6 degrees. A critical part of EME operation is knowing exactly where your antenna is pointing. ![]()
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